package train_string;

import java.util.Scanner;

public class Main {


    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        String[] str = sc.nextLine().split(" ");

        int len =0;
        for(int i = 0; i < str.length; i++) {
             len += str[i].length();
        }

        double  d = (double) len/str.length;
        System.out.println(String.format("%.2f", d));

    }
}
